CS>low sodium on blood test

[Paula Perry]

Does anyone know the significance of having low sodium on a blood test?  It is 
only slightly below normal. 134 with normal range being 135-148. I have had 
this reading on my last several blood tests. It is not from abstaining from 
salt or doing a lot of sweating. I am wondering if it couldn't indicate an 
adrenal insuffciency or other problem?
Thanks,
Paula